Positive cutting insert with compound clearance faces

Abstract

An polygonal indexable insert for use in periphery milling cutters. The insert is a positive insert having compound clearance faces comprised of a curve primary clearance surface adjacent the cutting edge and a planar secondary clearance surface adjacent the clearance edge of the insert. The curved primary clearance surface imparts improved strength to the cutting edge of the insert.

We claim: 
     
       1. A polygonal, indexable insert for peripheral rotary cutters comprising: a top surface, a planar bottom surface smaller than said top surface, and a side wall intersecting said bottom surface to define a clearance edge and extending outward from said bottom surface at an obtuse angle and intersecting said top surface to define a body; said intersection of said side wall and said top surface defining a cutting edge; said side wall comprised of side flank portions which extend from one corner of the insert to an adjacent corner of the insert; each side flank portion comprised of a primary clearance surface positioned adjacent to the cutting edge and a secondary clearance surface positioned adjacent to the bottom surface; said primary clearance surface being convexly curved in a direction from said cutting edge to a junction line some distance along said sidewall intermediate said top and bottom surface such that the primary clearance surface is curved in a direction transverse to a length of the cutting edge; said secondary clearance surface being planar and extending along said sidewall from said clearance edge to said junction line.   
     
     
       2. The insert of claim 1, wherein the top surface is convexly curved. 
     
     
       3. The insert of claim 1, wherein the junction line is substantially parallel to the cutting edge.